Problem with mouse and keyboard

So, I have an iMac 21.5 inch display and it's Late 2011 version. My problem is that when i open up the computer most of the times the left click of the mouse doesnt work and the keyboard also. Some times both of the clicks of the mouse doesnt work but still i can move the mouse around. So i just keep restarting the computer in order to make my keyboard and left click to work so i can use my password to unlock my imac and then go to the bootcamp program which i downloaded that allows me to restart my computer to windows that ive installed. The weird thing is that whenever im on windows both keyboard and mouse works perfectly which makes me think that there is a software problem around the mac os x. I want to point out that I tried the bluetooth keaboard and mouse of the imac but also keyboard and mouse that connects to the imac with usb. Whatever the keyboard and the mouse still the same problem. Can you somehow help me?

( Sorry about my bad english )

Thanks in advance,

George